This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
Ultrasound transducers are used to transmit and receive ultrasonic signals in a flowmeter system. Several problems were solved by using the present invention, they are: depressurizing the pipe gas line or the use of special tools for transducer replacement, poor transducer performance, and poor signal detection for gas meters at high flowrates. Current gas meters use gas wetted transducers since conventional transducer housings used in liquid meters cannot be used. Conventional liquid meter housings do not work in a gas environment for two reasons. First, conventional liquid transducer housings have thick metal windows that cannot transmit sound through gas. Second, the liquid transducer housings are traditionally welded to the meter body. This creates noise such that a received signal is poorly detected in a gas meter application. Wetted transducers are exposed to the gas which contains hydrogen sulfide. Hydrogen sulfide can overtime deteriorate transducers made of conventional solder joints and epoxies for electrical and mechanical connections within the transducer. In current gas meters, a metal seal is placed behind the transducer in order to maintain the pipe pressure and to prevent gas from leaking out. So if a transducer fails, the transducer has to be replaced using special tools that prevent the transducer from firing out of the flowmeter at high speeds due to pipe gas pressure. This may be deadly to the replacer if the tools are improperly handled because the transducer becomes a projectile under pipe gas pressure. If the gas pipeline has to be depressurized to replace transducers for safety reasons then the pipeline stops and revenue generated by its function is lost. Current gas meter transducers use either a monolithic PZT ceramic transducer or a Tonpilz transducer. These transducers suffer from poor bandwidth, poor signal to noise ratio and radial modes in the 100 to 300 kHz frequency range, the preferred operation ultrasonic frequency range for gas meters. As a result, the received signals can be very distorted and result in poor transit time measurements and poor accuracy of a gas flowmeter at high flow rates >60 feet/second. Current gas meters also have metal to metal contact between parts even with wetted transducers which cases are made of metal so the flow meter can suffer from poor signal to noise ratio due to acoustic noise of the system.